The pattern of isozymes of phenylalanine hydroxylase from liver and kidney of lower mammals and from liver of fetal and adult primate will be compared. We have been unable to demonstrate phenylalanine hydroxylase in primate kidney - but some conversion of C14 phenylalanine to DOPA was observed. An assay using a tyrosine hydroxylase inhibitor will be used to determine if activity can be demonstrated in kidney primates. Activity in inbred strains of mice will be compared in an attempt to find species with high and low levels of activity so the different species might be used to examine mechanisms of genetic control of production of the enzyme.